A first subject of the invention is that of the functionalization of silicones, in particular of linear polyorganosiloxanes (or POSs for short).
The functionalized POSs which are more specifically of interest in the context of the invention are multifunctionalized linear polyorganosiloxanes comprising alkoxyl polar functional groups and functional groups each having a thiol group SH.
These functional groups give the POSs specific properties which allow them to be used, for instance, and as form other subjects of the invention, as an anti-blocking modulator in silicone compositions or as a coating agent for a white filler, especially a siliceous filler, for the purpose of aiding the processing of the filler in filled silicone compositions and of allowing the silicone products obtained to be reinforced. These polyfunctionalized POSs can also be used as a white-filler/elastomer coupling agent in compositions of rubber(s) comprising a white filler, especially a siliceons substance, as a reinforcing filler.
The principle of POS multifunctionalization is described in document WO-A-96/16125 in the name of the Applicant. This document discloses, for example, the preparation of POSs comprising xe2x89xa1Sixe2x80x94(O-alkyl) functional units and xe2x89xa1Si-(chain having a sulphur-containing group, especially SH) functional units. The xe2x80x94(O-alkyl) functional group is introduced into an appropriate polyhydrogenoorganosiloxane by a dehydrogenocondensation reaction using alcohol from which the xe2x80x94(O-alkyl) functional group is derived (in this step, a fraction of the initial xe2x89xa1SiH groups is substituted by alkoxyl functional groups) and then the -(chain having a sulphur-containing group, especially SH) functional unit is introduced by hydrosilylation of an olefin carrying the sulphur-containing group by the remaining xe2x89xa1SiH groups.
Continuing work in this technical field, the Applicant has now discovered, and it is this which constitutes the first object of the invention, that it is possible to provide functional groups containing an SH group by making hydrogen sulphide react on a precursor multifunctionalized POS containing a specific reactive group which, in the presence of a catalyst, leads to an SH group; the group in question is an ethylenically unsaturated group located at the end of the chain or in the chain connected to a silicon atom.
Many documents exist in the prior art which describe the functionalization of ethylenically Unsaturated organic compounds by H2S; however, to the knowledge of the Applicant, it has never been a question, hence the novelty of the present invention, of the said reactions using appropriate functionalized POSs as raw material.